Chapter 5 Outline - Chapter 5 Outline I. The Nature of...

Chapter 5 Outline I. The Nature of Energy A. Energy- the capacity to do work or to transfer heat B. Work- the energy used to cause an object with matt to move against a force C. Heat- the energy used to cause the temperature of an object to increase II. Kinetic and Potential Energy A. Kinetic- the energy of motion A.i. E k = ½ mv 2 A.ii. Kinetic energy increases, as speed increases A.iii. For a given speed, the kinetic energy increases with increasing mass A.iv. Atoms and molecules have mass and are in motion—therefore have kinetic energy B. Potential- objects position relative to other objects B.i. All other kinds of energy besides kinetic—energy stores in chemical bonds, the energy attraction of north and south pole of magnets B.ii. Potential energy arises when a force operates on an object B.iii. E p = mgh B.iii.1. m = mass of the object in question, h = height of the object relative to some reference height, and g = the gravitational constant (9.8 m/s 2 ) B.iv. Electroslatatic potential energy- arises from the interactions between charged particles B.iv.1. E el is proportional to the electrical charges on the two interacting objects, Q 1 and Q 2 , and is inversely proportional to the distance separating them: B.iv.1.a. Eel = K Q 1 Q 2 d B.iv.1.b. K - is simply a constant of proportionality, 8.99 x 10 9 J-m/C2 B.iv.1.b.i. C is the coulomb, a unit of electrical charge, and J is the joule, a unit of energy B.iv.1.c. Q 1 and Q 2 when dealing w/ electrical charges are typically on the order of magnitude of the charge of the electron (1.60 x 10-19 C) B.iv.1.c.i. When Q 1 and Q 2 have the same sign, the two charges repel one another, pushing them apart; E el is positive B.iv.1.c.ii. When opposite signs, they attract one another, pulling them towards each other, E el is negative. C. Force- any kind of push or pull on an object C.i. Gravity D. Forms of energy are interconvertible E. The lower the energy of a system, the more stable it is E.i. The more strongly opposite charges interact, the more stable the system F. Chemical energy-is due to the potential energy stored in the arrangements of their atoms

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F.i. Energy a substance possesses because of its temperature (thermal energy) is associated with kinetic energy of the molecules in the substance III. Units of Energy A. Joule (J)- SI unit for energy A.i. 1 J = 1 kg-m 2 /s 2 A.ii. A joule is not a large amount of energy, kJ is often used instead B. calorie- 1 cal = 4.184 J C. Calorie- 1 Cal = 1000 cal = 1kcal IV. System and Surroundings A. System- portion we single out for study A.i. the reactants and products make up the system A.ii. Open system- matter and energy can be exchanged with the surroundings A.iii. Closed system- can exchange energy but not matter with its surroundings A.iv. Isolated system- neither energy or matter can be exchanged B. Surroundings- everything else V. Transferring Energy: Work and Heat A. Energy and heat are two ways that energy changes B. Work (w)- the energy transferred when a force moves an object

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